In manufacturing of a semiconductor device, a silicon oxide film is mainly used as an interlayer insulation film. As a method for forming the silicon oxide film, there is known a method for forming the film by CVD by using TEOS (tetraethyl orthosilicate), which is an organic silane-based gas, and an oxidizing agent. Currently, a silicon oxide film having a good film quality has been formed by plasma CVD using TEOS, and in particular, a silicon film oxide film having the same film quality as the thermal oxide film can be obtained by microwave plasma CVD. Accordingly, it has been examined that this technology is also applied to a gate insulation film which has been considered difficult to be applied to the conventional CVD.
However, currently, in accordance with size reduction or high integration of the semiconductor device, there are increasing cases where the silicon oxide film is formed on a recessed portion having a high aspect ratio. And in the CVD using TEOS, since a step coverage is poor, there is a problem in that it is difficult to form a film on a recessed portion having a high aspect ratio.
As a technology for obtaining a favorable step coverage by CVD using TEOS, Japanese Patent Application Laid-Open No. 2007-42884 (Patent Document 1) suggests a method for forming a silicon oxide film, in which a target object is placed in a processing vessel, and TEOS gas, oxygen gas and hydrogen gas are introduced into the processing vessel, the TEOS gas is then adsorbed on the target object while decomposition of TEOS gas in a gas phase is suppressed by heating the processing vessel under the reduced pressure atmosphere at a temperature lower than the decomposition temperature of the TEOS gas, and then, the adsorbed TEOS is decomposed to form a silicon oxide film.
However, since the C—C bonds existing in TEOS tend to be broken and active dangling bonds tend to be remained, TEOS is inherently apt to be attached. Accordingly, even though the same method as in Patent Document 1 is adopted, there is a limit to improve the step coverage. Therefore, there is a need for a starting material capable of forming a silicon oxide film having a better step coverage by a CVD method.